In underground mining and in other areas exposed to the danger of explosion or firedamp ignition, there is a need for the supply, independently of a power supply network, of sufficient intrinsically-safe voltage to electrical equipment. In underground mining, for example, a chargeable battery power supply that uses Nickel Cadmium storage battery cells (NiCad accumulators) is utilized for support shield controllers, remote controllers, measuring equipment in poorly-accessible areas and other electrical equipment. The NiCad storage batteries have a low charge capacity and poor recharging characteristics since, due to the so-called “memory effect”, reduced charging capacity results if the NiCad storage battery was not completely discharged before being recharged. Due to the low charging capacity of NiCad accumulators, a great number of spare storage batteries is required in underground mining that have to be taken underground and temporarily stored there. Recharging of the NiCad storage batteries takes place exclusively on the surface, wherein the transportation of charged and discharged storage batteries (accumulators) also represents a logistical problem.
In underground mining, power supply sources may only be used if they are certified for use in areas that are exposed to the danger of explosion and correspond with the ignition protection legislation (e.g. ATEX, IEC, Eex etc.) that is applicable in the place of utilization. Here, each approval examination is associated with substantial cost. Hence for reasons of cost, it is hardly possible to have repeatedly modified storage battery cells re-certified for use in areas that are exposed to the danger of explosion.
For this reason, intrinsically-safe battery power supplies are often used in underground mining that do not technologically correspond to the latest state of the art and whose basic structure is disclosed in DE 30 15 751 C2 from 1980. The battery power supplies comprise NiCad storage battery cells that are disposed in a battery housing and electronics, that are not intrinsically-safe, cast in silicon rubber and embedded in an electronics housing, wherein the two housings are inserted together in a master housing. Alternatively, the storage battery cells can be cast together with a necessary protection circuit to comply with the ignition protection class that is applicable to gain certification. Repair of such battery power supplies, especially the replacement of storage batteries within such battery power supplies, is not possible without unacceptable cost.
Outside the field of underground mining, especially in the field of the communications and entertainment industries, lithium storage battery cells (lithium accumulators) are increasingly replacing the lead-containing batteries and NiCad storage battery cells that have previously been used. Fundamental efforts are therefore being made to be able to use lithium storage battery cells in other areas of technology, as can be seen, for example, in U.S. Pat. No. 5,376,475 that relates to chargeable, aqueous lithium hydrogen ion batteries. There are, however, substantial safety problems associated with the use of lithium storage battery cells regarding possible explosion of the storage battery cells, as can be seen in U.S. Pat. No. 5,376,475. Up to now, lithium storage battery cells have therefore not been used in underground mining and other areas that are exposed to the danger of explosion.